Engines, for example vehicle engines, are being downsized and boosted, which is reducing the available vacuum from the engine. This vacuum has many potential uses, including use by the vehicle brake booster.
One solution to this vacuum shortfall is to install a vacuum pump. Vacuum pumps, however, have a significant cost and weight penalty to the engine, their electric power consumption can require additional alternator capacity, and their inefficiency can hinder fuel economy improvement actions.
Another solution is aspirators that generate vacuum by creating an engine air flow path that is parallel to the throttle, referred to as an intake leak. This leak flow passes through a Venturi that generates a suction vacuum. The problem with the presently available aspirators is that they are limited in the amount of vacuum mass flow rate they can generate, and by the amount of engine air they consume, for example, aspirators having a circular cross-section at the motive outlet end and the discharge inlet end as shown in FIG. 3 and as disclosed in U.S. Application Publication 2006/0016477 and U.S. Application Publication 2013/0213510.
A need exists for improved designs that generate increased vacuum pressure and increased suction mass flow rate while decreasing the consumption of engine air.